The invention relates to the operation of an expansion chamber of a pollution-free or depolluting engine with injection of additional compressed air.
In his published patent application WO 96/27737, the author has described a method for reducing pollution of an engine with an independent external combustion chamber operating on a dual-mode principle with two types of energy, using either conventional fuel of the gasoline or diesel oil type on the highway (in single-mode air-fuel operation) or, at low speed, particularly in towns and suburbs, with an addition of compressed air (or any other non-polluting gas) to the exclusion of any other fuel (so-called single-mode air-air operation, that is to say with the addition of compressed air). In his patent application WO 97/48884, the author has described the installing of this type of engine in single-mode operation on service vehicles, for example town buses, taxis or delivery vans.
In air-fuel mode, the air-fuel mixture is drawn into and compressed in an independent induction and compression chamber. This mixture is then transferred, still under pressure, to an independent and constant-volume combustion chamber where it is ignited in order to increase the temperature and pressure of the said mixture. Once a transfer port connecting the said combustion or expansion chamber to an expansion and exhaust chamber has opened, this mixture will be expanded in the latter chamber to produce work there. The expanded gases are then discharged to the atmosphere through an exhaust pipe.
When operating in air-air mode, at low power, the fuel injector is no longer operated; in this case, a small amount of additional compressed air from an external tank in which the air (or any other gas) is stored at high pressure, for example 200 bar, and at ambient temperature is introduced into the combustion chamber somewhat after the (fuel-free) compressed air from the induction and compression chamber has been let into this combustion chamber. Upon the injection of additional compressed air, this small amount of compressed air at ambient temperature will heat up in contact with the mass of high-temperature air contained in the combustion or expansion chamber, will expand and will increase the pressure obtaining in the chamber to allow work to be delivered upon expansion.
This type of dual-mode or dual-energy (air and gasoline or air and additional compressed air) engine can also be modified for preferential use, in town for example, on all vehicles and particularly on town buses or other service vehicles (taxis, trash-collecting trucks, etc.) in air-compressed air single mode by eliminating all the elements of the engine which operate in conjunction with the conventional fuel.
The engine then runs only in single mode with the injection of additional compressed air into the combustion chamber which thus becomes an expansion chamber. Furthermore, the air drawn in by the engine can be filtered or purified through one or more charcoal filters or using some other methodxe2x80x94mechanical, chemical, molecular sieve, or other filters in order to produce a depolluting engine. The use of the term xe2x80x9cairxe2x80x9d in the current text is to be understood as meaning xe2x80x9cany non-polluting gasxe2x80x9d.
In this type of engine, the additional compressed air is injected into the combustion or expansion chamber at a service pressure determined according to the pressure obtaining in the chamber and appreciably higher than this pressure. This entails relatively high injection pressures, for example of 30 bar.
The problems of the dynamics of the gases in fluid flows have been extensively studied and tested. In supersonic flows, the pressure waves emitted by the moving bodies form envelopes of shapes on the passage of which the air undergoes so-called very high-speed variations and physical properties which result in particular in the appearance of shock waves. Tests and experiments performed with a shock tube have been intended to carry out numerous experiments in the area of dynamics of gases and to determine their properties and in the area of supersonic wind tunnels (shock tunnels). A shock tube consists of two tube parts where a diaphragm is clamped between two ends and where the free ends are closed. One of the parts is known as the driving tube and the other part is known as the test tube and the entire entity is known as the shock tube. By filling the test tube with the gas on which tests are to be performed and by compressing the gas in the driving tube until the diaphragm bursts, a process of pressure equalization then ensues. The high-pressure driving gas expands in the form of an expansion wave and flows into the test tube. It therefore creates a shock wave in the low-pressure gas.
The method of operation of the expansion chamber according to the invention proposes the use of shock and shock wave techniques in subsonic and more particularly supersonic gaseous flows in order to get the best possible output from the engine by obtaining high pressures and temperatures of the gases in the expansion chamber before the said gas is transferred into the expansion and exhaust chamber. It consists in splitting the process of increasing the pressure in the chamber into two stages, by introducing a high-pressure driving gas from the induction and compression chamber into part of the said chamber and, on the other hand, by introducing the additional compressed air into the other part at a markedly lower pressure, then in suddenly bringing the two parts into contact to obtain, because of the pressure difference, a sudden expansion of the driving gas which expands in the form of an expansion wave and flows into the working gas at lower pressure, thereby creating a compression shock wave which makes it possible to considerably increase the total pressure in the chamber shortly before it expands in the expansion and exhaust chamber to produce work.
As a preference, the method of operation of the expansion chamber according to the invention involves ionization of the driving gas before it is introduced into the working chamber, which has the effect of creating waves of electromagnetic nature and of increasing the intensity of the shock wave in the working chamber and of delaying the relaxation phenomena.
The expansion chamber for the implementation of the method is divided into two parts separated by a very high-speed shutter which can bring them suddenly into communication at the chosen moment in the cycle; one of these chambers, known as the driving chamber, is connected to the induction and compression chamber and receives the driving gas therefrom; the second chamber is connected to the expansion and exhaust chamber and receives the additional compressed air; it thus becomes the working chamber. The operation of the expansion chamber according to the invention can thus be understood; first of all, the driving chamber is filled with hot compressed air at high pressure, for example 50 bar, from the induction and compression chamber, while an amount of additional compressed air from a storage tank under high pressure is injected so as to obtain a lower pressure, for example 10 bar, in the working chamber then, shortly before communication with the engine expansion cylinder, the inter-chamber shutter is suddenly opened; as a result, and because of the pressure difference, the driving gas will expand in the form of an expansion wave and will flow into the working chamber where it creates a compression shock wave and considerably increases the pressure in the said working chamber shortly before it is placed in communication with the expansion and exhaust cylinder. This increase in pressure is used to produce the work by expanding the gases in the expansion and exhaust chamber.
According to another feature of the invention, the shapes of the two chambers are in the form of nozzles where the driving chamber opens via a convergent section into a throat closed by a high-speed shutter which allows it to be opened suddenly at the chosen moment in the cycle, and onto the working chamber via a divergent section such that the supersonic jet created when the throat is opened causes the formation of vortexes, which, aside from the shock wave effects, make it possible to produce the desired pressure-increasing effects.
It is possible to calculate and choose the volumes of the driving chamber and of the working chamber, to optimize the shapes and sizes, to create one or more shocks triggering waves and/or vortexes without altering the method of the invention.
It is also possible, within the cycle, to choose the moment that the inter-chamber shutter opens and that the transfer into the expansion chamber occurs, so as to obtain the desired results, namely the highest possible pressure in the expansion chamber at the time of the expansion.